| Background Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD) and about 1/3-1/4 chronic dialysis patients are attributable to DN. Pathogenesis and current therapies of DN are limited, then how to retard the progression of DN becomes an emphasis. Improving glycemia, blood pressure control and reduction in protein intake have been shown to function in some of the patients. A low-protein diet (LPD) has been proposed to delay the progression of DN, but LPD predisposes these patients to deteriorate nutritional status that leads to high morbidity and mortality of atherosclerosis and cardiovascular disease. Ketoanalogues of amino acids (KAs) which are converted into essential amino acids in the body via transamination, are introduced to prevent nutritional deficiencies resulting from dietary protein restriction. However, the optimal dietary protein intake and KAs supplement in DN are still controversial.Objective To evaluate the short-term efficacy,safety profile of low-protein diet or very-low-protein diet (VLPD) supplemented with KAs in retarding the progression of DN.Methods We performed a prospective,randomized,open-label,controlled clinical trial. A total of 40 patients with DN with an estimated glomerular filtration rate (eGFR) of 30-90ml/min/1.73m2 were randomly assigned to two groups.LPD+KA group received 0.6 g protein/kg body weight/day and 0.12g ketoanalogues/kg body weight/day, and VLPD+KA group received 0.4 g protein/kg body weight/day and 0.2 g ketoanalogues/kg body weight/day. Both groups were adherent to the prescribed dietary protein intake restrictions and received a total caloric intake of 30 to 35 kcal/kg body weight/day. Exclusion criterias included failure to control the diet, liver dysfunction (AST or ALT two-fold as high as the normal level), other severe diseases (such as cancer, etc) or complicated with other kidney diseases (such as polycystic kidney disease, primary kidney disease, etc).The outcome measures were changes in eGFR (calculated by simplified MDRD formula),24h urine protein quantitative, blood biochemical indicators, blood fat, blood glucose, parathyroid hormone (PTH), glycosylated hemoglobin (HbA1C), insulin dosage and so on.The patients were followed for 12 months. In the first three months,we examined our patients once a month,and then once every three months. We had an assessment after one year,and then readjusted our plan on the basis of results.Results (1) Intra-group comparisons of the measures (mean±SD) before and after the treatment in LPD+KA group and VLPD+KA group:eGFR did not changed (P＞0.05), serum ureas significantly decreased (P＜0.01), hypocalcemias were corrected (P＜0.05), serum phosphates and PTH significantly decreased (P＜0.01),fast plasma glucose and postprandial 2h plasma glucose were controlled well, HbAlc decreased (P＜0.05),proteinuria levels started to decline during the first month (P＜0.05) and reached their lowest level at 3months (P＜0.01). No significant changes in any of the parameters of the nutritional status such as albumin, prealbumin, transferrin, triglyceride, cholesterol, body mass index (BMI) were noted (P＞0.05). (2) Inter-group comparisons of the measures (mean±SD) before and after the treatment in LPD+KA group and VLPD+KA group:all the parameters had no statistically significant differences (P＞0.05). (3) No adverse reactions were noted in LPD+KA group and VLPD+KA group.Conclusion Over a 12-month period, both LPD+KA and VLPD+KA seemed to help DN patients to ameliorate nitrogen waste products retention, calcium-phosphorus metabolism disturbances, secondary hyperparathyroidism, glucose metabolism and decrease proteinuria levels. Both LPD+KA and VLPD+KA were safe and tolerable in retarding the progression of renal failure and preserving the nutritional status of DN patients,but the differences between two groups were not obvious, then the optimal dietary protein intake and KA supplement in DN remained inconclusive and needed future studies.
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